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Old Jan 21, 2015, 08:06 AM
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Power and trust to weight ratio for F-15

Hi,

I am sure this have been asked many times before however me looking at the threads I cannot get a straight answer or at least make my mind up if my thought are correct. So bare with me

I am in the process of building a depron (6mm) F-15 based on Shumate's design. I would like to install two 50mm EDF units but based on what I can get in the market, the weight will increase to around 35oz.

Am I right to believe that if I have a thrust to weight ration of 1:1 this will be sufficient to make the plane to fly comfortably without struggling? I have found a apir of EDFs in Hobbyking(Hobbyking 50mm Alloy EDF V2 4200kv) that will give a max thrust of 550g that I believe that is more than sufficient. The power of each unit is around 330W each which is more than enough to go over the usual threshold of 100W/lb.

I would greatly appreciate any thoughts on this

Michael
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Last edited by mace04; Jan 21, 2015 at 08:06 AM. Reason: Spelling mistake
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Old Jan 21, 2015, 10:31 AM
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A 1 to 1 is always nice but not needed. many jets can fly with only 30% thrust and 50% and up will fly well. A lot will depend on other aspects of the design as to how well the plane flys. like airfoil type and wing loading.. Thrust to weight is not a real good way to est how a plane flys. it just means it will be fast or slow. So for you weight may be a bigger factor with wing loading not thrust
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Old Jan 22, 2015, 10:02 AM
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Thanks turbonut.

Based on the plans I am basing my construction the wing loading is 9.2 oz/sq ft for an AUW of around 16oz. I would assume this changes if I double the weight of the plane?

My main concern is doubling the weight of the plane in order to accommodate for 2 EDF units and the power needed on the back of that.
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Last edited by mace04; Jan 22, 2015 at 11:50 AM.
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Old Jan 22, 2015, 12:35 PM
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At 9.2 it will be pretty much a floater..at 20 oz it will be more jet like but will fly well
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